A known prior art package sorting device includes a bar code reader and a conveying means running in a straight line over a low-friction surface for conveying parcels to a plurality of intermediate destinations. The parcels are classified by means of the bar code reader, and are then routed by dragging each parcel across a plurality of trap doors which, upon command, may be opened to allow the parcels to discharge into respective containers, bags or onto further conveyor belts. The known conveying means consists of substantially quadrangular-shaped openings arranged in a conveyor belt with a diagonal of each opening aligned with the feed direction of the belt itself. The parcels to be sorted come from a feed chute and are dropped into one of the quadrangular openings where, due to the feed motion of the conveyor belt, each parcel is held in a predetermined position defined by the two sides of the quadrangular opening which are opposite the feed direction of the belt and which serve to drag the parcels over the underlying low-friction surface which is disposed under the conveyor belt.
Because devices of the type mentioned above utilize belts running in a straight line over a rectilinear surface, the sorting installations cannot extend over a large distance unless a number of such devices are coupled one to another in an in-line arrangement. Such an in-line arrangement of several conveyor belts poses certain technical problems, especially in the vicinity of the junction or interface between one conveyor belt and the next one in line. In fact, due to the cylindrical shape of the head rollers of the conveyor belts, a gap or trough is present between the two adjacent belts which may cause misalignment of, or even overturn, a parcel, making bar code identification by any downstream readout means impossible. Moreover, connecting several sorting lines by means of in-line coupled belts leads inevitably to difficulties in maintaining the proper synchronization both of the feed motion of the belts relative to one another, and of the opening of each the various trap doors relative to its associated belt. Finally, such in-line sorting devices cannot utilize the conveyor belt during its return trip to the feed chute because the belt is then inverted relative to the low-friction surface.